A speaker apparatus in which a dome type diaphragm is supported by a frame through an edge damper integrated with an outer periphery thereof has been spread for a vehicle-mounted audio apparatus or for a portable apparatus since an angle of emitting sound is wider than that of a speaker apparatus using a cone type diaphragm, a stable sound field can be formed by a wide angle and the speaker apparatus is suitable for small-sized formation.
A development of an elliptical shape dome speaker apparatus using an outer peripheral shape of a diaphragm in an oval shape or an elliptical shape is remarkable as a dome type diaphragm since the speaker apparatus achieves an excellent low region reproducing characteristic by gaining an area of the diaphragm even in a narrow installing space particularly for a small-sized portable apparatus.
According to a speaker apparatus using the dome type diaphragm, a method of adjusting a compliance (deformability=flexibility) of an edge damper is known as a method of setting a low sound resonance frequency (fo) to a desired value.
In a related art, a compliance of the edge damper is adjusted by changing a width (edge width), a height (roll height), a material thickness of a damper main body. The damper main body is integrated to an outer periphery of a diaphragm and is deformed in accordance with an amplitude of the diaphragm.
However, the width or the height or the material thickness of the damper main body cannot be changed by large amounts. It is difficult to promote a degree of freedom or adjusting the compliance.
Hence, as shown by FIG. 1, it is proposed to form reinforcing ribs 7 at a damper main body 5 of an edge damper 3 integrated to an outer periphery of a dome type diaphragm 1 at predetermined intervals in a peripheral direction (refer to, for example, JP-A-2004-48494 and JP-A-2002-271887).
According to the dome type diaphragm 1 shown in FIG. 1, a shape of an outer periphery of the diaphragm is oval.
The edge damper 3 is constituted by the damper main body 5 deformed in correspondence with amplitude of the diaphragm formed in a sectional shape of a roll-like shape, and an attaching flange portion 9 extended to an outer periphery thereof and fixed to an edge attaching portion of a frame.
The reinforcing rib 7 is a groove portion or a ridge portion formed at the damper main body 5 by pressing. The reinforcing rib 7 is formed by a pertinent length to be along a width direction of the damper main body 5 in a range of the damper main body 5 excluding a vicinity of an inner peripheral portion thereof and a vicinity of an outer peripheral portion thereof.
According to the reinforcing rib 7, a compliance of the edge damper 3 can be adjusted even by adjusting an interval of mounting the reinforcing ribs 7, a length dimension of the reinforcing rib 7 or the like. A degree of freedom of adjusting the compliance can be promoted. Accordingly, an adjustment of a low sound resonance frequency (fo) is facilitated.
Further, as a speaker apparatus using a dome type diaphragm, in order to strengthen a rigidity of a dome portion, a reinforcing rib is provided at an outer peripheral edge of a diaphragm fixed with a voice coil, so that a disturbance in a high region frequency characteristic is reduced by a harmonic distortion (refer to, for example, JP-A-5-183986 and JP-A-11-355883).